The invention relates to an electronic control unit for a motor vehicle equipped with a plurality of data networks and an electronic immobilizer.
It is an increasing tendency for vehicles today to be equipped with an electronic immobilizer. In addition to simple systems which interrupt the engine starting process, the fuel pump relay and/or the ignition via a relay, more advanced systems involve a direct data communication between the electronics of the immobilizer and an engine controller, this communication usually being achieved via a databus, such as a CAN-bus. The immobilizer is usually initialized from an electronic key, either via remote control or via a transponder in the key in conjunction with an induction coil.
This arrangement provides a high degree of protection against theft, in particular when high-quality data exchange codes, protected on a cryptological basis, are used; it also requires a certain degree of electronic complexity. An example of such a modern immobilizer is the system described in the German Patent Application P 44 11 451.6-51. The additional electronics for the immobilizer of course entails additional possible failures, the result of which could be an unintended situation in which the vehicle can no longer be started even by the person authorized to do so.
On the other hand, in modern vehicles, data networks are frequently used for the communication of the electronic vehicle components with one another. These networks can have very different structures, for example star-shaped structures are frequently realized, in which the various networks are linked in a control unit, frequently the so-called combined instrument which primarily serves to control the display and control elements. In early systems, in such contexts at maximum specific isolated signals were transmitted from one network to the other.
Networks which permit a complete signal transmission between the individual connected networks via a so-called gateway are considered to be advanced. For example, the realization of the gateway in a central control unit or in the combined instrument has been proposed in the literature. In the case of a motor vehicle described in German patent document DE 41 10 372 A1, three networks are provided, one for diagnostic purposes, one for control unit networking and one for vehicle accessories, such as switches and measuring instruments. The three networks are connected to one another with a gateway which can be configured as a stand-alone module between the three networks or can be accommodated in a network node of one of the networks.
An object of the present invention is to provide an electronic control unit for a motor vehicle with a plurality of data networks and an electronic immobilizer, which can be used to provide the immobilizer function and a gateway function for the networks with relatively little outlay.
Another object of the invention is to provide the conditions which permit the immobilizer to be given a redundant configuration with little additional outlay.
These and other objects and advantages are achieved according to the invention by the combination of the gateway and vehicle-end control section of the immobilizer in a single control unit. This arrangement permits multiple use of electronic components in the control unit so that the outlay on components can be reduced in comparison with a separate realization of these two functions.
In a particularly advantageous embodiment of the invention, redundancy for the vehicle-end control section of the immobilizer is achieved so that the probability of an unintended situation in which the vehicle can no longer be started owing to a failure of the vehicle-end control section of the immobilizer is significantly reduced in comparison with immobilizer systems which do not have a redundant configuration.
Another embodiment of the invention realizes a control unit design containing, with relatively few components, a gateway, a vehicle-end control section for the immobilizer and a redundant immobilizer control section which is parallel to the latter. As many components as possible are used doubly, on the one hand for the gateway and on the other hand for the immobilizer. In particular, the two microprocessors which are required for the gateway are used for the two immobilizer control sections 80, so that separate microprocessors are not required for the latter.
In a preferred positioning of the combination of the gateway and vehicle-end immobilizer control section in an electronic ignition starter switch, the ignition starter switch performs not only its normal ignition starter control function, a gateway function, and a control function for the immobilizer; it also provides redundancy of the immobilizer function.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.